Nicholas Scott

University of Sydney, Sydney, New South Wales, Australia

Are you Nicholas Scott?

Claim your profile

Publications (76)250.97 Total impact

  • Alister W. Graham, Nicholas Scott
    [Show abstract] [Hide abstract]
    ABSTRACT: Several recent papers have reported on the occurrence of active galactic nuclei (AGN) containing under-massive black holes relative to a linear scaling relation between black hole mass (M_bh) and host spheroid stellar mass (M_sph,*). Dramatic revisions to the M_bh-M_sph,* and M_bh-L_sph relations, based on samples containing predominantly inactive galaxies, have however recently identified a new steeper relation at M_bh < (2-10)x10^8 M_Sun, roughly corresponding to M_sph,* < (0.3-1)x10^{11} M_Sun. We show that this steeper, quadratic-like M_bh-M_sph,* relation defined by the Sersic galaxies, i.e. galaxies without partially depleted cores, roughly tracks the apparent offset of the AGN having 10^5 < M_bh/M_Sun < 0.5x10^8. That is, these AGN are not randomly offset with low black hole masses, but also follow a steeper (non-linear) relation. As noted by Busch et al., confirmation or rejection of a possible AGN offset from the steeper M_bh-M_sph,* relation defined by the Sersic galaxies will benefit from improved stellar mass-to-light ratios for the spheroids hosting these AGN. Several implications for formation theories are noted. Furthermore, reasons for possible under- and over-massive black holes, the potential existence of intermediate mass black holes (<10^5 M_Sun), and the new steep (black hole)--(nuclear star cluster) relation, M_bh ~ (M_nc)^{2.7+/-0.7}, are also discussed.
    12/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using black hole masses which span 10^5 to 10^(10) solar masses, the distribution of galaxies in the (host spheroid stellar mass)-(black hole mass) diagram is shown to be strongly bent. While the core-Sersic galaxies follow a near-linear relation, having a mean M_(bh)/M_(sph) mass ratio of ~0.5%, the Sersic galaxies follow a near-quadratic relation: M_bh~M_sph^(2.22+\-0.58). This is not due to offset pseudobulges, but is instead an expected result arising from the long-known bend in the M_(sph)-sigma relation and the log-linear M_(bh)-sigma relation.
    11/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We take advantage of the first data from the Sydney-AAO Multi-object Integral field (SAMI) Galaxy Survey to investigate the relation between the kinematics of gas and stars, and stellar mass in a comprehensive sample of nearby galaxies. We find that all 235 objects in our sample, regardless of their morphology, lie on a tight relation linking stellar mass ($M_{*}$) to internal velocity quantified by the $S_{0.5}$ parameter, which combines the contribution of both dispersion ($\sigma$) and rotational velocity ($V_{rot}$) to the dynamical support of a galaxy ($S_{0.5}=\sqrt{0.5V_{rot}^{2}+\sigma^{2}}$). Our results are independent of the baryonic component from which $\sigma$ and $V_{rot}$ are estimated, as the $S_{0.5}$ of stars and gas agree remarkably well. This represents a significant improvement compared to the canonical $M_{*}$ vs. $V_{rot}$ and $M_{*}$ vs. $\sigma$ relations. Not only is no sample pruning necessary, but also stellar and gas kinematics can be used simultaneously, as the effect of asymmetric drift is taken into account once $V_{rot}$ and $\sigma$ are combined. Our findings illustrate how the combination of dispersion and rotational velocities for both gas and stars can provide us with a single dynamical scaling relation valid for galaxies of all morphologies across at least the stellar mass range 8.5$<log(M_{*}/M_{\odot})<$11. Such relation appears to be more general and at least as tight as any other dynamical scaling relation, representing a unique tool for investigating the link between galaxy kinematics and baryonic content, and a less biased comparison with theoretical models.
    The Astrophysical Journal Letters 10/2014; 795(2). · 6.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Galactic archeology based on star counts is instrumental to reconstruct the past mass assembly of Local Group galaxies. The development of new observing techniques and data-reduction, coupled with the use of sensitive large field of view cameras, now allows us to pursue this technique in more distant galaxies exploiting their diffuse low surface brightness (LSB) light. As part of the Atlas3D project, we have obtained with the MegaCam camera at the Canada-France Hawaii Telescope extremely deep, multi--band, images of nearby early-type galaxies. We present here a catalog of 92 galaxies from the Atlas3D sample, that are located in low to medium density environments. The observing strategy and data reduction pipeline, that achieve a gain of several magnitudes in the limiting surface brightness with respect to classical imaging surveys, are presented. The size and depth of the survey is compared to other recent deep imaging projects. The paper highlights the capability of LSB--optimized surveys at detecting new prominent structures that change the apparent morphology of galaxies. The intrinsic limitations of deep imaging observations are also discussed, among those, the contamination of the stellar halos of galaxies by extended ghost reflections, and the cirrus emission from Galactic dust. The detection and systematic census of fine structures that trace the present and past mass assembly of ETGs is one of the prime goals of the project. We provide specific examples of each type of observed structures -- tidal tails, stellar streams and shells --, and explain how they were identified and classified. We give an overview of the initial results. The detailed statistical analysis will be presented in future papers.
    10/2014;
  • The Astrophysical Journal. 09/2014; 792(2):L37.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the Atlas3D project. We study trends between our dynamically-derived IMF normalisation and absorption line strengths, and interpret these via single stellar population- (SSP-) equivalent ages, abundance ratios (measured as [alpha/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalisation of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of normalisation at a given population parameter. As a result, we find weak IMF-[alpha/Fe] and IMF-age correlations, and no significant IMF-[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalisation via low-mass star demographics inferred through stellar spectral analysis.
    08/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We use the Atlas3D sample to perform a study of the intrinsic shapes of early-type galaxies, taking advantage of the available combined photometric and kinematic data. Based on our ellipticity measurements from the Sloan Digital Sky Survey Data Release 7, and additional imaging from the Isaac Newton Telescope, we first invert the shape distribution of fast and slow rotators under the assumption of axisymmetry. The so-obtained intrinsic shape distribution for the fast rotators can be described with a Gaussian with a mean flattening of q=0.25 and standard deviation sigma_q = 0.14, and an additional tail towards rounder shapes. The slow rotators are much rounder, and are well described with a Gaussian with mean q = 0.63 and sigma_q =0.09. We then checked that our results were consistent when applying a different and independent method to obtain intrinsic shape distributions, by fitting the observed ellipticity distributions directly using Gaussian parametrisations for the intrinsic axis ratios. Although both fast and slow rotators are identified as early-type galaxies in morphological studies, and in many previous shape studies are therefore grouped together, their shape distributions are significantly different, hinting at different formation scenarios. The intrinsic shape distribution of the fast rotators shows similarities with the spiral galaxy population. Including the observed kinematic misalignment in our intrinsic shape study shows that the fast rotators are predominantly axisymmetric, with only very little room for triaxiality. For the slow rotators though there are very strong indications that they are (mildly) triaxial.
    08/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The SAMI Galaxy Survey will observe 3400 galaxies with the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) on the Anglo-Australian Telescope (AAT) in a 3-year survey which began in 2013. We present the throughput of the SAMI system, the science basis and specifications for the target selection, the survey observation plan and the combined properties of the selected galaxies. The survey includes four volume limited galaxy samples based on cuts in a proxy for stellar mass, along with low-stellar mass dwarf galaxies all selected from the Galaxy And Mass Assembly (GAMA) survey. The GAMA regions were selected because of the vast array of ancillary data available, including ultraviolet through to radio bands. These fields are on the celestial equator at 9, 12, and 14.5 hours, and cover a total of 144 square degrees (in GAMA-I). Higher density environments are also included with the addition of eight clusters. The clusters have spectroscopy from 2dFGRS and SDSS and photometry in regions covered by the Sloan Digital Sky Survey (SDSS) and/or VLT Survey Telescope/ATLAS. The aim is to cover a broad range in stellar mass and environment, and therefore the primary survey targets cover redshifts 0.004 < z < 0.095, magnitudes r$_{pet}$ < 19.4, stellar masses $10^{7} - 10^{12}$ M$_{sol}$, and environments from isolated field galaxies through groups to clusters of $10^{15}$ M$_{sol}$.
    07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the Early Data Release of the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. The SAMI Galaxy Survey is an ongoing integral field spectroscopic survey of ~3400 low-redshift (z<0.12) galaxies, covering galaxies in the field and in groups within the Galaxy And Mass Assembly (GAMA) survey regions, and a sample of galaxies in clusters. In the Early Data Release, we publicly release the fully calibrated datacubes for a representative selection of 107 galaxies drawn from the GAMA regions, along with information about these galaxies from the GAMA catalogues. All datacubes for the Early Data Release galaxies can be downloaded individually or as a set from the SAMI Galaxy Survey website. In this paper we also assess the quality of the pipeline used to reduce the SAMI data, giving metrics that quantify its performance at all stages in processing the raw data into calibrated datacubes. The pipeline gives excellent results throughout, with typical sky subtraction residuals of 0.9-1.2 per cent, a relative flux calibration uncertainty of 4.1 per cent (systematic) plus 4.3 per cent (statistical), and atmospheric dispersion removed with an accuracy of 0."09, less than a fifth of a spaxel.
    07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a methodology for the regularisation and combination of sparse sampled and irregularly gridded observations from fibre-optic multi-object integral-field spectroscopy. The approach minimises interpolation and retains image resolution on combining sub-pixel dithered data. We discuss the methodology in the context of the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) Galaxy Survey underway at the Anglo-Australian Telescope. The SAMI instrument uses 13 fibre bundles to perform high-multiplex integral-field spectroscopy across a one degree diameter field of view. The SAMI Galaxy Survey is targeting 3000 galaxies drawn from the full range of galaxy environments. We demonstrate the subcritical sampling of the seeing and incomplete fill factor for the integral-field bundles results in only a 10% degradation in the final image resolution recovered. We also implement a new methodology for tracking covariance between elements of the resulting datacubes which retains 90% of the covariance information while incurring only a modest increase in the survey data volume.
    07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We examine the kinematic morphology of early-type galaxies (ETGs) in three galaxy clusters Abell 85, 168 and 2399. Using data from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) we measured spatially-resolved kinematics for 79 ETGs in these clusters. We calculate $\lambda_{R}$, a proxy for the projected specific stellar angular momentum, for each galaxy and classify the 79 ETGs in our samples as fast or slow rotators. We calculate the fraction of slow rotators in the ETG populations ($f_{SR}$) of the clusters to be $0.21\pm0.08$, $0.08\pm0.08$ and $0.12\pm0.06$ for Abell 85, 168 and 2399 respectively, with an overall fraction of $0.15\pm0.04$. These numbers are broadly consistent with the values found in the literature, confirming recent work asserting that the fraction of slow rotators in the ETG population is constant across many orders of magnitude in global environment. We examine the distribution of kinematic classes in each cluster as a function of environment using the projected density of galaxies: the kinematic morphology-density relation. We find that in Abell 85 $f_{SR}$ increases in higher density regions but in Abell 168 and Abell 2399 this trend is not seen. We examine the differences between the individual clusters to explain this. In addition, we find slow rotators on the outskirts of two of the clusters studied, Abell 85 and 2399. These galaxies reside in intermediate to low density regions and have clearly not formed at the centre of a cluster environment. We hypothesise that they formed at the centres of groups and are falling into the clusters for the first time.
    Monthly Notices of the Royal Astronomical Society 06/2014; 443(1). · 5.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present photospheric-phase observations of LSQ12gdj, a slowly-declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude $M_B = -19.8$, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23800 \AA) light curve out to 45 days past $B$-band maximum light. We estimate that LSQ12gdj produced $0.96 \pm 0.07$ $M_\odot$ of $^{56}$Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27% of the flux at the earliest observed phases, and 17% at maximum light, is emitted bluewards of 3300 \AA. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 \AA, and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, up to 10% of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius $< 10^{13}$ cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.
    04/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present measurements of the star formation rate (SFR) in the early-type galaxies (ETGs) of the ATLAS3D sample, based on Wide-field Infrared Survey Explorer (WISE) 22um and Galaxy Evolution Explorer (GALEX) far-ultraviolet emission. We combine these with gas masses estimated from 12CO and HI data in order to investigate the star formation efficiency (SFE) in a larger sample of ETGs than previously available. We first recalibrate (based on WISE data) the relation between old stellar populations (traced at Ks-band) and 22um luminosity, allowing us to remove the contribution of 22um emission from circumstellar dust. We then go on to investigate the position of ETGs on the Kennicutt-Schmidt (KS) relation. Molecular gas-rich ETGs have comparable star formation surface densities to normal spiral galaxy centres, but they lie systematically offset from the KS relation, having lower star formation efficiencies by a factor of ~2.5 (in agreement with other authors). This effect is driven by galaxies where a substantial fraction of the molecular material is in the rising part of the rotation curve, and shear is high. We show here for the first time that although the number of stars formed per unit gas mass per unit time is lower in ETGs, it seems that the amount of stars formed per free-fall time is approximately constant. The scatter around this dynamical relation still correlates with galaxy properties such as the shape of the potential in the inner regions. This leads us to suggest that dynamical properties (such as shear or the global stability of the gas) may be important second parameters that regulate star formation and cause much of the scatter around star-formation relations.
    03/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present integral field spectroscopy of 10 early-type galaxies in the nearby, low-mass, Fornax cluster, from which we derive spatially resolved stellar kinematics. Based on the morphologies of their stellar velocity maps we classify 2/10 galaxies as slow rotators, with the remaining 8 galaxies fast rotators. Supplementing our integral field observations with morphological and kinematic data from the literature, we analyse the `kinematic' type of all 30 galaxies in the Fornax cluster brighter than M_K = -21.5 mag (M_* ~ 6 x 10^9 M_sun). Our sample's slow rotator fraction within one virial radius is 7(^+4_-6) per cent. 13(^+8_-6} per cent of the early-type galaxies are slow rotators, consistent with the observed fraction in other galaxy aggregates. The fraction of slow rotators in Fornax varies with cluster-centric radius, rising to 16(^+11_-8) per cent of all kinematic types within the central 0.2 virial radii, from 0 per cent in the cluster outskirts. We find that, even in mass-matched samples of slow and fast rotators, slow rotators are found preferentially at higher projected environmental density than fast rotators. This demonstrates that dynamical friction alone cannot be responsible for the differing distributions of slow and fast rotators. For dynamical friction to play a significant role, slow rotators must reside in higher mass sub-halos than fast rotators and/or form in the centres of groups before being accreted on to the cluster.
    03/2014; 441(1).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: One quarter of all nearby early-type galaxies (ETGs) outside Virgo host a disc/ring of HI with size from a few to tens of kpc and mass up to ~1e+9 solar masses. Here we investigate whether this HI is related to the presence of a stellar disc within the host making use of the classification of ETGs in fast and slow rotators (FR/SR). We find a large diversity of HI masses and morphologies within both families. Surprisingly, SRs are detected as often, host as much HI and have a similar rate of HI discs/rings as FRs. Accretion of HI is therefore not always linked to the growth of an inner stellar disc. The weak relation between HI and stellar disc is confirmed by their frequent kinematical misalignment in FRs, including cases of polar and counterrotating gas. In SRs the HI is usually polar. This complex picture highlights a diversity of ETG formation histories which may be lost in the relative simplicity of their inner structure and emerges when studying their outer regions. We find that LCDM hydrodynamical simulations have difficulties reproducing the HI properties of ETGs. The gas discs formed in simulations are either too massive or too small depending on the star formation feedback implementation. Kinematical misalignments match the observations only qualitatively. The main point of conflict is that nearly all simulated FRs and a large fraction of all simulated SRs host corotating HI. This establishes the HI properties of ETGs as a novel challenge to simulations.
    01/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a study of the cold gas contents of the Atlas3D early-type galaxies, in the context of their optical colours, near-UV colours, and H\beta\ absorption line strengths. Early-type (elliptical and lenticular) galaxies are not as gas-poor as previously thought, and at least 40% of local early-type galaxies are now known to contain molecular and/or atomic gas. This cold gas offers the opportunity to study recent galaxy evolution through the processes of cold gas acquisition, consumption (star formation), and removal. Molecular and atomic gas detection rates range from 10% to 34% in red sequence early-type galaxies, depending on how the red sequence is defined, and from 50% to 70% in blue early-type galaxies. Notably, massive red sequence early-type galaxies (stellar masses > 5e10 Msun, derived from dynamical models) are found to have HI masses up to M(HI)/Mstar ~ 0.06 and H_2 masses up to M(H$_2$)/Mstar ~ 0.01. Some 20% of all massive early-type galaxies may have retained atomic and/or molecular gas through their transition to the red sequence. However, kinematic and metallicity signatures of external gas accretion (either from satellite galaxies or the intergalactic medium) are also common, particularly at stellar masses <= 5e10 Msun, where such signatures are found in ~ 50% of H$_2$-rich early-type galaxies. Our data are thus consistent with a scenario in which fast rotator early-type galaxies are quenched former spiral galaxies which have undergone some bulge growth processes, and in addition, some of them also experience cold gas accretion which can initiate a period of modest star formation activity. We discuss implications for the interpretation of colour-magnitude diagrams.
    12/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present new Spectrographic Areal Unit for Research on Optical Nebulae (SAURON) integral-field spectroscopy and Swift Ultraviolet Optical Telescope (UVOT) observations of molecular outflow host galaxy NGC 1266 that indicate NGC 1266 has experienced a rapid cessation of star formation. Both the SAURON maps of stellar population age and the Swift UVOT observations demonstrate the presence of young ($< 1$ Gyr) stellar populations within the central 1 kpc, while existing Combined Array for Research in Millimeter-wave Astronomy (CARMA) CO(1--0) maps indicate that the sites of current star formation are constrained to the inner few hundred parsecs of the galaxy only. The optical spectrum of NGC 1266 from Moustakas & Kennicutt (2006) reveal a characteristic post-starburst (K+A) stellar population and Davis et al. (2012) confirm that ionized gas emission in the system originate from a shock. Galaxies with K+A spectra and shock-like ionized gas line ratios may comprise an important, overlooked segment of the post-starburst population, containing exactly those objects in which the AGN is actively expelling the star-forming material. While AGN activity is not the likely driver of the post-starburst event that occurred 500 Myr ago, the faint spiral structure seen in the Hubble Space Telescope (HST) Wide-field Camera 3 (WFC3) Y-, J- and H-band imaging seems to point to the possibility of gravitational torques being the culprit. If the molecular gas were driven into the center at the same time as the larger scale galaxy disk underwent quenching, the AGN might be able to sustain the presence of molecular gas for $\gtrsim 1$ Gyr by cyclically injecting turbulent kinetic energy into the dense molecular gas via a radio jet, inhibiting star formation.
    The Astrophysical Journal 11/2013; 780(2). · 6.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a detailed two-dimensional stellar dynamical analysis of a sample of 44 cosmological hydrodynamical simulations of individual central galaxies and their satellites. Kinematic maps of the stellar line-of-sight velocity, velocity dispersion, and higher-order Gauss-Hermite moments $h_3$ and $h_4$ are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the $\lambda_{\mathrm{R}}$-parameter. The velocity, velocity dispersion, $h_3$, and $h_4$ fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS$^{\rm{3D}}$ survey. This includes fast (regular), slow, and misaligned rotation, hot spheroids with embedded cold disk components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a significant influence on the rotation properties resulting in both a spin-down as well as a spin-up of the merger remnant. Lower mass galaxies with significant in-situ formation of stars, or with additional gas-rich major mergers - resulting in a spin-up - in their formation history, form elongated fast rotators with a clear anti-correlation of $h_3$ and $v/\sigma$. An additional formation path for fast rotators includes gas poor major mergers leading to a spin-up of the remnants. This formation path does not result in anti-correlated $h_3$ and $v/\sigma$. The galaxies most consistent with the rare class of non-rotating round early-type galaxies grow by gas-poor minor mergers alone. In general, more massive galaxies have less in-situ star formation since $z \sim 2$, rotate slower and have older stellar populations. (shortened)
    11/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present integral-field spectroscopy of 27 galaxies in the Coma cluster observed with the Oxford SWIFT spectrograph, exploring the kinematic morphology-density relationship in a cluster environment richer and denser than any in the ATLAS3D survey. Our new data enables comparison of the kinematic morphology relation in three very different clusters (Virgo, Coma and Abell 1689) as well as to the field/group environment. The Coma sample was selected to match the parent luminosity and ellipticity distributions of the early-type population within a radius 15' (0.43 Mpc) of the cluster centre, and is limited to r' = 16 mag (equivalent to M_K = -21.5 mag), sampling one third of that population. From analysis of the lambda-ellipticity diagram, we find 15+-6% of early-type galaxies are slow rotators; this is identical to the fraction found in the field and the average fraction in the Virgo cluster, based on the ATLAS3D data. It is also identical to the average fraction found recently in Abell 1689 by D'Eugenio et al.. Thus it appears that the average slow rotator fraction of early type galaxies remains remarkably constant across many different environments, spanning five orders of magnitude in galaxy number density. However, within each cluster the slow rotators are generally found in regions of higher projected density, possibly as a result of mass segregation by dynamical friction. These results provide firm constraints on the mechanisms that produce early-type galaxies: they must maintain a fixed ratio between the number of fast rotators and slow rotators while also allowing the total early-type fraction to increase in clusters relative to the field. A complete survey of Coma, sampling hundreds rather than tens of galaxies, could probe a more representative volume of Coma and provide significantly stronger constraints, particularly on how the slow rotator fraction varies at larger radii.
    Monthly Notices of the Royal Astronomical Society 08/2013; 436(1). · 5.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: According to a popular scenario supported by numerical models, the mass assembly and growth of massive galaxies, in particular the Early-Type Galaxies (ETGs), is, below a redshift of 1, mainly due to the accretion of multiple gas-poor satellites. In order to get observational evidence of the role played by minor dry mergers, we are obtaining extremely deep optical images of a complete volume limited sample of nearby ETGs. These observations, done with the CFHT as part of the ATLAS3D, NGVS and MATLAS projects, reach a stunning 28.5 - 29 mag.arcsec-2 surface brightness limit in the g' band. They allow us to detect the relics of past collisions such as faint stellar tidal tails as well as the very extended stellar halos which keep the memory of the last episodes of galactic accretion. Images and preliminary results from this on-going survey are presented, in particular a possible correlation between the fine structure index (which parametrizes the amount of tidal perturbation) of the ETGs, their stellar mass, effective radius and gas content.
    Proceedings of the International Astronomical Union 07/2013;

Publication Stats

397 Citations
250.97 Total Impact Points

Institutions

  • 2014
    • University of Sydney
      • Sydney Institute of Astronomy (SIfA)
      Sydney, New South Wales, Australia
  • 2012–2014
    • Swinburne University of Technology
      • Centre for Astrophysics and Supercomputing
      Melbourne, Victoria, Australia
  • 2013
    • South African Astronomical Observatory
      Kaapstad, Western Cape, South Africa
  • 2009–2012
    • University of Oxford
      • Department of Physics
      Oxford, ENG, United Kingdom
    • University of Texas at Austin
      • Department of Astronomy
      Texas City, TX, United States
  • 2010–2011
    • Leiden University
      • Leiden Observartory
      Leiden, South Holland, Netherlands